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Quartz-sericite and argillic alterations at the Peschanka Cu-Mo-Au deposit, Chukchi Peninsula, Russia
Article in Geology of Ore Deposits · May 2015 DOI: 10.1134/S1075701515030034
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Ivan Baksheev A. F. Chitalin Lomonosov Moscow State University INSTITUTE OF GEOTECHNOLOGY LLC, Moscow, Russia
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Ildar Kalko Vsevolod Yuriyevich Prokof’ev Lomonosov Moscow State University Russian Academy of Sciences
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The user has requested enhancement of the downloaded file. ISSN 1075 7015, Geology of Ore Deposits, 2015, Vol. 57, No. 3, pp. 213–225. © Pleiades Publishing, Ltd., 2015. Original Russian Text © L.I. Marushchenko, I.A. Baksheev, E.V. Nagornaya, A.F. Chitalin, Yu.N. Nikolaev, I.A. Kal’ko, V.Yu. Prokofiev, 2015, published in Geologiya Rudnykh Mestorozhdenii, 2015, Vol. 57, No. 3, pp. 239–252.
Quartz–Sericite and Argillic Alterations at the Peschanka Cu–Mo–Au Deposit, Chukchi Peninsula, Russia L. I. Marushchenkoa, I. A. Baksheeva, E. V. Nagornayab, A. F. Chitalinc, Yu. N. Nikolaeva, I. A. Kal’koa, and V. Yu. Prokofievd a Mocow State University, Moscow, 119234 Russia b Vernadsky State Geological Museum, Russian Academy of Sciences, ul. Mokhovaya 11, str. 11, Moscow, 125009 Russia c Regional Mining Company LLC, ul. Sadovnicheskaya 4, Moscow, 115035 Russia d Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Staromonetny per. 35, Moscow, 119017 Russia Received July 22, 2014
Abstract—The porphyry Peschanka copper–molybdenum–gold deposit and the Nakhodka ore field located in the Baimka ore trend on the western Chukchi Peninsula are spatially related to monzonitic rocks of the Early Cretaceous Egdykgych Complex. Two types of quartz–sericite metasomatic rocks (QSR) have been identified at both the deposits and the ore field: (I) chlorite–quartz–muscovite rock with bornite and chal copyrite (porphyry type) and (II) tourmaline–quartz–carbonate–muscovite ± phengite rock accompanied by veins with base metal mineralization (subepithermal or transitional type), as well as carbonate–quartz– illite rock (argillic alteration) accompanied by veins with precious metal mineralization (epithermal type). The QSR I chlorite evolves from chamosite to clinochlore, which is caused by increasing H2S activity in min eralizing fluid and precipitation of sulfide minerals. The QSR I clinochlore is significantly depleted in silica as compared with that from the rocks affected by argillic alteration. The chemical composition of muscovite from both quartz–sericite alterations is similar. The QSR II carbonates evolve from calcite through dolomite to siderite, which results from the increasing activity of CO2 followed by the decreasing activity of H2S in min eralizing fluid. The Mn content in dolomite is similar to that in beresite (quartz–muscovite–carbonate– pyrite metasomatic rock) of the intrusion related gold deposits. Illite from argillic alteration is depleted in Al as compared with that of postvolcanic epithermal Au–Ag deposits. However, carbonates from the discussed argillic alteration rhodochrosite and Mn rich dolomite are similar to those from quartz–illite rock at postvol canic epithermal Au–Ag deposits. DOI: 10.1134/S1075701515030034
INTRODUCTION Several types of alteration are conventionally iden tified at porphyry copper deposits: biotite–potassium Porphyry deposits are the main source of copper all feldspar–quartz (potassic), propylitic, quartz–seric over the world. In Russia, these deposits are located in ite, and argillic. The first type of alteration forms an the Ural, Kuznetsk Alatau, Eastern Syan, Chukotka, internal zone of metasomatic aureole with negligible Sikhote Alin, and Kamchatka folded areas. The larg Cu–Mo mineralization. The outer zone is barren pro est deposits in Russia are Aksug in Tuva and Peschanka pylitic. The quartz–sericite alteration are located in the Chukchi Peninsula; the latter, along with the within the potassic zone and localized above it, Nakhodka ore field (NOF), is situated in the Baimka accompanying the porphyry mineralization. Epither Cu–Mo–Au trend located 200 km south of Bilibino. mal precious metal mineralization is spatially related This trend comprises four porphyry copper fields to argillic alteration. In addition, the carbonate–base (from north to south): Yuryakh (YOF), Peschanka metal mineralization frequently developed at por (total copper reserves about 6 Mt) Nakhodka (copper phyry molybdenum–copper deposits (Corbett and reserves about 3 Mt) (Chitalin et al., 2013), and Leach, 1998) is regarded as transitional from porphyry Omchak, which were discovered in the late 1960 to to the epithermal stage. Sillitoe (2010) has proposed early 1970s and were explored up to early 1990s (Migachev, 1984; Migachev et al., 1995; Kaminskii, calling it subepithermal. At most porphyry copper 1989; Shapovalov, 1990; Volchkov, 1982). Prospecting deposits related to granodiorite, this type of mineral